Abscisic Acid Inhibits Asymbiotic Germination of Immature Seeds of Paphiopedilum armeniacum

Abstract

Paphiopedilum armeniacum is a rare orchid native to China with high ornamental value. The germination of P. armeniacum seeds is difficult, especially for the mature seeds, which is the major limitation for their large-scale reproduction. This study explored the reasons for seed germination inhibition from the aspects of the important plant endogenous hormone—abscisic acid (ABA). The major endogenous hormone contents of seeds were determined at different developmental stages. The ABA content was 5.8 ng/g in 73 days after pollination (DAP) for the immature seeds, peaked at 14.6 ng/g in 129 DAP seeds, and dropped to 2.6 ng/g in the late mature stage of the 150 DAP seeds. The reduction of ABA content in the mature seed suggests a possible contribution to the increased expression of CYP707A, an ABA catabolism gene. The germination rate of the immature seeds was reduced to 9% from 69% when 5 μg/mL ABA was added to the Hyponex N026 germination medium. The result showed that ABA can inhibit the germination of P. armeniacum immature seeds. However, for the heavily lignified mature seeds, reduction in endogenous ABA level does not result in an increase in the germination rate. Lignin accumulation in the seed coat imposes the physical dormancy for P. armeniacum. In summary, the germination of P. armeniacum is regulated by both ABA and lignin accumulation.

The orchid embryo — “an embryonic protocorm”

“…In Calanthe tricarinata (Lee et al 2007) and Cypripedium formosanum (Lee et al 2005), the ABA levels stay high during seed maturation. Moreover, in Paphiopedilum armeniacum, the levels decrease during the final stages of seed maturation (Xu et al 2020).…”

“…at the time of seed maturation (Yan et al 2017). Recently, Xu et al (2020) profiled the major endogenous hormone levels in Paphiopedilum armeniacum using high-performance liquid chromatography-mass spectroscopy. They also noted an increase in auxin levels after pollination and early stages of seed development, then followed by a decline.…”

EFFECT OF ADDING PEPTONE IN ACCELERATING GERMINATION OF Grammatophyllum stapeliiflorum J.J. Smith IN VITRO

“…Kandungan IAA yang tinggi akan mendorong pembentukan embrio zigotik menjadi embrio globular (Ningsih dan Sudiyono, 2018). Perkecambahan tertinggi terjadi ketika embrio globular terbentuk (Xu et al, 2020).…”

Comparative transcriptomics and proteomics analysis of the symbiotic germination of Paphiopedilum barbigerum with Epulorhiza sp. FQXY019

“…The traditional propagation of Paphiopedilum orchids using an axillary bud division from the mother plant is unproductive and time-consuming ( Chen et al, 2004 ). Many Paphiopedilum seeds form a compatible and symbiotic relationship with mycorrhizal or endophytic fungi that facilitates their germination in conditions of their natural habitat ( Xu et al, 2020 ; Li Y. Y. et al, 2021 ). During this process, regarded as symbiotic germination, fungi and seeds form a nonphotosynthetic spherical body named a protocorm, which completely relies on mycorrhizal fungi for nourishment ( Fang et al, 2021 ).…”